Conventionally, a rotational angle detection apparatus for detecting the rotational angle of a rotating body has been used in a variety of applications. As this kind of rotational angle detection apparatus, an apparatus has been known that is provided with a magnet fixed so as to rotate integrally with the rotating body, and a magnetic sensor element for detecting changes in the intensity of a magnetic field accompanying rotation of the magnet. In such a rotational angle detection apparatus, the magnetic sensor element outputs a signal indicating the relative positional relationship between the rotating body and the magnetic sensor element.
As a conventional rotational angle detection apparatus, as shown in FIG. 37A and FIG. 37B, an apparatus has been known in which a magnet 200 formed in a disk shape is supported by and fixed to a shaft S (axis of rotation) such that a first surface 201 and a second surface 202 of the magnet 200 are orthogonal to the shaft S (axis of rotation), and magnetic sensor elements (Hall elements) 300 are positioned directly below the outer perimeter of the second surface 202 of the magnet 200 and in a circumferential direction centered on the shaft S (axis of rotation), (see Patent Literature 1).
In the above-described rotational angle detection apparatus, there are cases in which the magnet 200 supported by and fixed to the shaft S (axis of rotation) moves slightly in a radial direction, due to axial shaking occurring in which the shaft S (axis of rotation) moves slightly in a radial direction. On the other hand, the magnetic sensor element (Hall element) 300 is positioned to measure the magnetic flux density in a direction parallel to the shaft S (axis of rotation), at the corner of the outer perimeter of the magnet 200. Consequently, the problem exists that accompanying slight movements of the magnet 200, the measured value of the magnetic flux density measured by the magnetic sensor element (Hall element) 300 fluctuates greatly, and the measurement error in the angle of rotation becomes large.
Hence, conventionally, as shown in FIG. 38A and FIG. 38B, a rotational angle detection apparatus has been proposed in which a magnet 210 is supported by and fixed to the shaft S (axis of rotation) and includes a first surface 211 and a second surface 212 which is opposed to the first surface 211 and a magnetic sensor element (Hall element) 310 is positioned directly below the outer perimeter edge of the magnet 210. The magnet 210 includes a chamfer 213 (inclined surface) formed by removing a corner of the outer perimeter edge of the first surface 211 side over the entire perimeter. The magnet 210 is arranged such that a portion of the detection surface of the magnetic sensor element (Hall element) 310 is positioned directly below the chamfer 213 (inclined surface), and the remaining portion is positioned to the outside of the outer perimeter edge of the magnet 210 (see Patent Literature 2).